Disperse dyeing of textile fibers

ABSTRACT

A process for dyeing textile fibers employs a colorant medium comprising a disperse dye and an aqueous dispersion of a copolymer selected from vinyl ester-based copolymers, alkyl acrylate copolymers, alkyl methacrylate copolymers and mixtures thereof. The textile fibers are passed through at least one dye bath containing the colorant medium to deposit the colorant medium at least on the surface of the fibers. The fibers with the colorant medium deposited thereon are then passed between padding rollers to distribute the colorant medium through the fibers, whereafter the fibers are heated to cure the copolymer and bond the disperse dye to the fibers.

FIELD

The present development relates to the dyeing of textile fibers, particularly cellulosic fibers and especially cotton fibers, with disperse dyes. Background

Cotton fibers in the form of yarns and fabrics have generally been dyed with reactive, direct, sulfur, vat, indigo or mordant dyes. Currently the industry prefers reactive dyeing for apparel as reactive dyes provide the brightest colored cotton of all the dyes. Water-soluble reactive dyes, which also provide dyeing results with good fastness-to-washing properties, can be used to dye or print hydrophilic cellulose fibers such as cotton fibers. In such procedures, the cellulose fiber —OH groups which are accessible on the fiber surface react with the fiber-reactive groups of the reactive dyes, forming a covalent fiber/dye bond.

Direct or substantive dyes are used in a neutral or slightly alkaline dye bath with the addition of sodium chloride or sodium sulfate. Vat dyes such as indigo are essentially insoluble in water. Reduction in alkaline liquor produces the water soluble alkali metal salt of a vat dye, which salt has an affinity for textile fibers such as cotton. Both direct and vat dyes provide for dull shades which limits their ability to expand into all cotton dyeing applications.

Dyeing of cotton with reactive dyes gives good color fastness. However, reactive dyes are strongly hydrophilic leading to dye wastage and process inefficiencies and high costs due to the necessity of using long dyeing times with salt additions and alkali, thus allowing for the sensitive needs of reactives for high pH and high temperature conditions. Reactive dyes which do not react with cotton cellulose in the dyeing step eventually react with water and hydrolyze. This hydrolyzed dye must be removed from the cotton surface after dyeing with an after-soaping step to improve crockfastness and washfastness properties. Reactive dyes are also currently under scrutiny as possibly being cancer-causing agents.

Another dye class commonly employed for the coloring of textiles comprises disperse dyes. Disperse dyes were originally developed for the dyeing of cellulose acetate and are water-insoluble. Disperse dyes are finely ground in the presence of a dispersing agent. The main use of disperse dyes is for the dyeing of polyester, but they can also be used to dye nylon, cellulose acetate and acrylic fibers. Dyeing of polyester with disperse dyes requires a temperature of 130° C. provided through an exhaust (batch) machine capable of high pressure (such as a jet machine) or a continuous process with a stenter frame (See Thermasol process).

Given their lack of affinity or substantivity for cellulose, disperse dyes cannot be readily used to dye cotton fibers and fabrics. However, some attempts have been made to provide procedures for dyeing modified cotton fibers, e.g., fabrics, with disperse dyes. For example, U.S. Patent Publication No. 2006/0048308 discloses a method of dyeing or printing cellulose-containing fiber materials using disperse dyes. Such a method comprises pre-treating the cellulose fiber material with a water-soluble or dispersible polyester resin and a water-soluble or dispersible acrylic binder. The polyester resin is fixed, for example, to cotton fabric with the acrylic binder and strong cross-linkers (e.g., melamine) via a pretreatment bath. The polyester impregnated fabric is then dyed with an aqueous dye bath containing disperse dye at a temperature of 130° C. under elevated pressure conditions. However, the high levels of resin binder required in this process adversely affects the softness of the dyed fabric.

In addition, International Patent Publication No. WO2012/135622 discloses a process for dyeing cotton-containing textile fibers, in which the fibers are initially treated with a cellulose-reactive emulsion copolymer in order to provide a combination of emulsion copolymer and fibers. The combination of emulsion copolymer and fibers is then cured to chemically anchor the emulsion copolymer to the cotton fibers via reaction of the cellulose-reactive monomers within the copolymer with cellulose hydroxyl moieties within the cotton fibers, to thereby form copolymer-treated cotton fibers. The copolymer-treated cotton fibers are then contacted with a disperse dye material under conditions which are sufficient to affix the disperse dye material to the copolymer component of the copolymer-treated cotton fibers.

However, whereas the process of the '522 Publication produces dyed cotton fabrics having excellent crockfastness, lightfastness and washfastness, without impairing the softness of the fabric, it would be desirable to provide a single-bath process for dispersed dyeing cotton fabrics, especially using a continuous padding process.

SUMMARY

In one aspect, the present development is directed to a process for dyeing textile fibers, the process comprising:

-   -   (a) providing at least one dye bath comprising a colorant medium         comprising a disperse dye and an aqueous dispersion of a         copolymer selected from vinyl ester-based copolymers, alkyl         acrylate copolymers, alkyl methacrylate copolymers and mixtures         thereof;     -   (b) passing the textile fibers through the at least one dye bath         to deposit the colorant medium at least on the surface of the         fibers;     -   (c) passing the fibers with the colorant medium deposited         thereon between padding rollers to distribute the colorant         medium through the fibers; and then     -   (d) heating the fibers to cure the copolymer and bond the         disperse dye to the fibers

Conveniently, the textile fibers comprise natural fibers, preferably cellulosic fibers, more preferably cotton fibers, optionally together with synthetic fibers.

In one embodiment, the copolymer comprises vinyl acetate and ethylene, such as comprises from 60 wt % to 95 wt % of vinyl acetate and from 5 wt % to 50 wt % of ethylene, based on total weight of monomers therein.

In another embodiment, the copolymer comprises an alkyl acrylate and/or an alkyl methacrylate containing 1 to 12, preferably 1 to 10, carbon atoms in the alkyl group, optionally together with acrylonitrile.

In one embodiment, the colorant medium comprises from 0.01 wt % to 15 wt % of the disperse dye. In addition, the colorant medium may have a solids content from about 2 wt % to about 10 wt %, more preferably from 3 wt % to 6 wt %, and pH from 2 to 8.

Conveniently, the temperature of the colorant medium during step (b) is from 10° C. to 50° C. and the textile fibers are passed through the dye bath at a rate of from 1 m/min to 70 m/min.

In one embodiment, the padding rollers apply a pressure from 50 to 250 kPa to the textile fibers during step (c).

Conveniently, the heating (d) is conducted at a temperature from 100° C. to 200° C. for a period (dwell time) of from 0.2 to 4 minutes and produces a dyed textile fiber product comprising from 0.1 to 10 wt %, preferably from 1 to 8 wt %, more preferably from 3 wt % to 6 wt %, of the copolymer on a dry basis based on the combined weight of the copolymer and the textile fibers.

In one embodiment, the fibers are continuously passed from step (b) to step (d).

DETAILED DESCRIPTION

The present development is directed to the dyeing of textile fibers in the form of yarn, fabric or garments, by padding from a dye bath containing both a disperse dye and an aqueous dispersion of a curable copolymer binder followed by curing of the binder to bond the dye to fibers. In this way, even when the fibers are formed mostly or totally of a cellulosic material, such as cotton, a wash fast and light fast dyed product can be produced using a single padding/curing sequence, rather than an initial binder application and curing, followed by a separate batch exhaust dyeing step. The present process allows the continuous pad dyeing of textile fiber materials with disperse dyes using a single dye bath.

Textile Fibers

The term “textile fibers” is used herein to individual staple fibers or filaments (continuous fibers), yarns, fabrics, and articles (e.g., garments). Yarns may include, for instance, multiple staple fibers that are twisted together (“spun yarn”), filaments laid together without twist (“zero-twist yarn”), filaments laid together with a degree of twist, and a single filament with or without twist (“monofilament”). The yarn may or may not be texturized. Suitable fabrics may likewise include, for instance, woven fabrics, knit fabrics, and non-woven fabrics. Garments may be apparel and industrial garments. The terms “fabrics” and “textiles” also include home goods such as linens, drapery, and upholstery (automotive, boating, airline included) made of the cotton fibrous materials described herein. The present process is, however, particularly applicable to the continuous pad dyeing of rolls of textile material and elongated webs of fibers.

Any type of textile fiber can be used with the present dyeing process but the process is particularly applicable to natural fibers, such as cotton, wool, bast, silk, etc., especially cellulosic fibers and most particularly cotton fibers. In some cases it may be desirable to employ a combination of natural fibers with synthetic fibers, such as aromatic polyamides (e.g., meta-aramids (e.g., Nomex® or Kevlar®), para-aramids, etc.), aliphatic polyamides (e.g., nylon), polyesters, polybenzimidazole (“PBI”), polybenzoxazole (“PBO”), polypyridobisimidazole (“PIPD”), rayon, melamine, acrylic (acrylonitrile) , acetate, lyocell, etc., as well as combinations of two or more types of natural and/or synthetic fibers. In general, it is preferred that the textile fibers employed herein contain at least 25 wt %, such as at least 50 wt %, for example at least 60 wt % of cotton fibers.

Disperse Dyes

The present process employs disperse dye material as a dyeing agent. Disperse dyes were originally developed for the dyeing of cellulose acetate and are water-insoluble. They are generally finely ground in the presence of a dispersing agent (surfactant) and are sold as a paste or spray-dried and sold as a powder.

Suitable disperse dyes for use in the dyeing method herein are those described under “Disperse Dyes” in the Colour Index, 3rd edition (3rd revision 1987 inclusive of Additions and Amendments up to No. 85). Such dyes include, for example, carboxylic acid group-free and/or sulfonic acid group-free nitro, amino, aminoketone, ketoninime, methine, polymethine, diphenylamine, quinoline, benzimidazole, xanthene, oxazine and coumarin dyes and especially anthraquinone and azo dyes, such as mono- or di-azo dyes. Such disperse dyes are also those described in detail in U.S. Patent Publication No. 2006/0048308. That '308 patent document, and especially its disclosure of the several structural formulas for disperse dye materials disclosed therein, is incorporated herein by reference.

Examples of commercially available primary red color disperse dyes include Disperse Red 60 (Intrasil Brilliant Red 2B 200%), Disperse Red 50 (Intrasil Scarlet 2GH), Disperse Red 146 (Intrasil Red BSF), Disperse Red 127 (Dianix Red BSE), Dianix Red ACE, Disperse Red 65 (Intrasil Red MG), Disperse Red 86 (Terasil Pink 2 GLA), Disperse Red 191 (Intrasil Pink SRL), Disperse Red 338 (Intrasil Red 4BY), Disperse Red 302 (Tetrasil Pink 3G), Disperse Red 13 (Intrasperse Bordeaux BA), Disperse Red 167 (Foron Rubine S-2GFL), and Disperse Violet 26 (Intrasil Violet FRL). Examples of commercially available primary blue color disperse dyes include Disperse Blue 60 (Terasil Blue BGE 200%), Disperse Blue 291 (Intrasil Blue MGS), Disperse Blue 118 (Terasil Blue GBT), Terasil Blue HLB, Dianix Blue ACE, Disperse Blue 87 (Intrasil Blue FGB), Disperse Blue 148 (Palnnil Dark blue 3RT), Disperse Blue 56 (Intrasil Blue FBL), and Disperse Blue 332 (Bafixan Turquoise 2 BL liq.). Examples of commercially available primary yellow color dyes include Disperse Yellow 64 (Disperite Yellow 3G 200%), Disperse Yellow 23 (Intrasil Yellow 5R), Palanil Yellow HM, Disperse Brown 19 (Dispersol Yellow D-7G), Disperse Orange 30 (Foron Yellow Brown S-2RFL), Disperse Orange 41 (Intrasil Orange 4RL), Disperse Orange 37 (Intrasil Dark Orange 3GH), Disperse Yellow 3, Disperse Orange 30, Disperse Yellow 42, Disperse Orange 89, Disperse Yellow 235, Disperse Orange 3, Disperse Yellow 54, Disperse Yellow 233 (Foron Yellow S-6GL),

The preferred types of disperse dye materials useful herein include the quinoline dyes, the anthraquinone dyes and the azo dyes. The dyeing method herein is equally useful with disperse dyes whether they are classified as high energy dyes, medium energy dyes or low energy dyes. Useful disperse dyes which can be used herein also include dyes which are especially formulated for to serve as automotive dyes, lightfast dyes or fluorescent dyes

Polymer Binder

In the present process, the disperse dye is combined with an aqueous dispersion of a curable copolymer capable of acting as a binder between the fibers and the disperse dye material. Generally, suitable polymers are emulsion copolymers and particularly cellulose-reactive aqueous emulsion copolymers, including those which have conventionally been used as textile finishing agents. Such emulsion copolymers include those described in detail in U.S. Patent Publication No. 2011/0005008, the entire contents of which are incorporated by reference herein.

Suitable types of cellulose-reactive emulsion copolymers for use in the present method herein include vinyl ester-based, acrylic-based, styrene/acrylic-based and styrene/butadiene-based emulsion copolymers. Such copolymers typically can also contain minor amounts of cross-linking or emulsion stabilizing co-monomers. Such co-monomers can, for example, in and of themselves or in combination with external cross-linking agents, make the emulsion copolymers used herein cellulose-reactive. Other potentially useful polymers are water-based polyurethanes, aqueous fluoropolymer emulsions, water-based alkyd resins and aqueous emulsions of halogenated polymers (e.g., vinyl chloride, vinylidene chloride, chloroprene, chlorostyrene, etc.).

One preferred type of emulsion copolymer comprises the vinyl ester-based copolymers selected from vinyl acetate-ethylene copolymers, vinyl acetate-vinyl alkanoate copolymers; vinyl acetate-acrylic copolymers, and combinations of these copolymer types. Vinyl acetate-ethylene (VAE) emulsion copolymers are well-known. Such VAE copolymers useful herein can comprise from about 60 wt % to about 95 wt % of vinyl acetate and from about 5 wt % to about 40 wt % of ethylene, based on total monomers therein. More preferably, VAE copolymers will comprise from about 70 wt % to about 90 wt % of vinyl acetate and from about 8 wt % to about 15 wt % of ethylene, based on total monomers therein.

Another preferred type of emulsion copolymer for use in the method herein comprises acrylic emulsion copolymers made of acrylic ester co-monomers. The alkyl acrylates that can be used to prepare the acrylic ester copolymer emulsions include alkyl acrylates and alkyl methacrylates containing 1 to 12, preferably 1 to 10 carbon atoms in the alkyl group. The polymer backbone in the acrylic ester copolymer can be either hydrophilic or hydrophobic and it can comprise polymerized soft monomers and/or hard monomers. The soft and hard monomers are monomers which, when polymerized, produce soft or hard polymers, or polymers in between. Preferred soft acrylic ester monomers are selected from alkyl acrylates containing 2 to 8 carbon atoms in the alkyl group and include ethyl acrylate, propyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate. The hard acrylic ester monomers are selected from alkyl methacrylates containing up to 3 carbon atoms in the alkyl group and from non-acrylic monomers such as styrene and substituted styrenes, acrylonitrile, vinylchloride, and generally any compatible monomer the homopolymer of which has a Tg above 50° C. Preferred acrylic ester monomers are selected from alkyl acrylates and methacrylates containing 1 to 12 carbon atoms in the alkyl group, especially ethyl acrylate and butyl acrylate.

In one embodiment, the copolymer binder is produced from a monomer composition comprising at least 80 weight %, such as at least 85 weight %, of alkyl acrylate or alkyl methacrylate monomers and up to 20% by weight, such as from 5 to 15% by weight, for example from 6 to 12%, by weight, of acrylontrile, both percentages being based on the total weight of the monomer composition.

The copolymer binder will frequently contain, in addition to the main monomers, minor amounts of co-monomers which can provide cross-linking with both cellulose hydroxyl moieties within the cotton fibers and cross-linking within the polymer itself. Such cross-linking co-monomers are unsaturated so as to polymerize into the polymer backbone and will also contain at least one functional group such as nitrogen, oxygen and/or silicon atoms.

Thus the polymer binder used herein can comprise from about 0.1 wt % to about 10 wt %, such as from about 0.5 wt. % to about 8 wt. %, for example from about 1 wt. % to about 6 wt. %, based on total monomers in the polymer, of one or more ethylenically unsaturated cross-linking co-monomers having, for example, at least one amide, epoxy, or alkoxysilane group. Specific examples of such co-monomers include, for instance, acrylamides, such as N-methylolacrylamide (NMA), N-methylolmethacrylamide, diacetoneacrylamide, etc., as well as esters or ethers thereof, such as isobutoxy ethers or esters of N-methylolacrylamide, of N-methylolmethacrylamide. Also suitable are epoxide-functional co-monomers, such as glycidyl methacrylate, glycidyl acrylate, allyl glycidyl ether, vinyl glycidyl ether, etc. Further examples are silicon-functional co-monomers, such as acryloxy-propyltri(alkoxy)silanes and methacryloxy-propyltri(alkoxy)silanes, vinyltrialkoxysilanes and vinylmethyldialkoxysilanes, with alkoxy groups which can be present being, for example, methoxy, ethoxy and ethoxypropylene glycol ether radicals. Yet other suitable crosslinking co-monomers have hydroxy and/or carboxyl groups, such as hydroxyalkyl methacrylates and acrylates (e.g., hydroxyethyl, hydroxypropyl or hydroxybutyl acrylate or methacrylate), acetylacetoxyethyl acrylate or methacrylate, dimethylaminoethyl acrylate, etc.

The polymer binder can also contain, in addition to the main monomers and self cross-linking co-monomers, minor amounts of multifunctional external cross-linking co-monomers. Thus the copolymers used herein can optionally comprise from about 0.1 wt % to about 10 wt %, based on total monomers in the copolymer, of one of more of these multifunctional cross-linking co-monomers. Suitable external crosslinking agents may also include phenol formaldehyde resins, resorcinol formaldehyde resins, melamine formaldehyde resins, hydroxymethylsubstituted imidazolidinones or thioimidazolidinones, hydroxymethyl substituted pyrimidinones or hydroxymethyl substituted triazinones or glycoluriles or their self-condensation products are suitable or mixed condensates from two or more of the compounds mentioned, or a mixture from two or more of the compounds mentioned. When employed, such crosslinking agents are typically combined with the polymer after it is formed.

Preferably, the copolymer binder used in the present process contains less than 25 wt %, preferably less than 10 wt %, of a polyester, and most preferably contains substantially no polyester.

The polymer binders used herein can frequently be selected from commercially available aqueous copolymer dispersions. Alternatively, suitable cellulose-reactive copolymers can be prepared in conventional fashion using known emulsion polymerization techniques and raw materials. In general, such emulsion copolymers can be prepared by polymerizing appropriate co-monomers in appropriate amounts in an aqueous reaction mixture using conventional polymerization initiators and catalysts and conventional polymerization conditions. Suitable polymerization processes are described in the Kirk-Othmer Encyclopedia of Chemical Technology, 4^(th) Ed Vol. 24, pp. 954-963 (Wiley 1996). The copolymer emulsions so prepared can be stabilized with conventional emulsifiers (surfactants) and/or protective colloids.

In certain embodiments, light stabilizers can also be employed in the polymer binder to help improve the lightfastness of a dye that is applied to the fibers. Without intending to be limited by theory, it is believed that when crosslinked, the emulsion copolymer coating can help disperse and encapsulate the light stabilizer around the fiber so that it is not easily removed or degraded. When employed, light stabilizers may constitute from about 0.1 wt. % to about 10 wt. %, in some embodiments from about 0.2 wt. % to about 5 wt. %, and in some embodiments, from about 0.25 wt. % to about 4 wt. % of the polymer coating.

One particularly suitable light stabilizer that may be employed is a hindered amine light stabilizer (“HALS”). Suitable HALS compounds may be derived from a substituted piperidine, such as alkyl-substituted piperidyl, piperidinyl, piperazinone, alkoxypiperidinyl compounds, and so forth. For example, the hindered amine may be derived from a 2,2,6,6-tetraalkylpiperidinyl. The hindered amine may, for example, be an oligomeric or polymeric compound having a number average molecular weight of about 1,000 or more, in some embodiments from about 1000 to about 20,000, in some embodiments from about 1500 to about 15,000, and in some embodiments, from about 2000 to about 5000. Such compounds typically contain at least one 2,2,6,6-tetraalkylpiperidinyl group (e.g., 1 to 4) per polymer repeating unit. One particularly suitable high molecular weight hindered amine is commercially available from Clariant under the designation Hostavin® N30 (number average molecular weight of 1200). Another suitable high molecular weight hindered amine is commercially available from Adeka Palmarole SAS under the designation ADK STAB® LA-63 and ADK STAB® LA-68. Yet other examples of suitable high molecular weight hindered amines include, for instance, an oligomer of N-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol and succinic acid (Tinuvin® 622 from Ciba Specialty Chemicals, MW=4000); oligomer of cyanuric acid and N,N-di(2,2,6,6-tetramethyl-4-piperidyl)-hexamethylene diamine; poly((6-morpholine-S -triazine-2,4-diyl) (2,2,6,6-tetramethyl-4-piperidinyl)-iminohexamethylene-(2,2,6,6-tetramethyl-4-piperidinyl)-imino) (Cyasorb® UV 3346 from Cytec, MW=1600); polymethylpropyl-3-oxy-[4(2,2,6,6-tetramethyl)-piperidinyl)-siloxane (Uvasil® 299 from Great Lakes Chemical, MW=1100 to 2500); copolymer of α-methylstyrene-N-(2,2,6,6-tetramethyl-4-piperidinyl)maleimide and N-stearyl maleimide; 2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-diethanol tetramethyl-polymer with 1,2,3,4-butanetetracarboxylic acid; and so forth. Still other suitable high molecular weight hindered amines are described in U.S. Pat. Nos. 5,679,733 to Malik, et al. and 6,414,155 to Sassi, et al.

In addition to the high molecular hindered amines, low molecular weight hindered amines may also be employed. Such hindered amines are generally monomeric in nature and have a molecular weight of about 1000 or less, in some embodiments from about 155 to about 800, and in some embodiments, from about 300 to about 800. Specific examples of such low molecular weight hindered amines may include, for instance, bis-(2,2,6,6-tetramethyl-4-piperidyl) sebacate (Tinuvin® 770 from Ciba Specialty Chemicals, MW=481); bis-(1,2,2,6,6-pentamethyl-4-piperidinyl)-(3,5-ditert.butyl-4-hydroxybenzyl)butyl-propane dioate; bis-(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate; 8-acetyl-3-dodecyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro-(4,5)-decane-2,4-dione; butanedioic acid-bis-(2,2,6,6-tetramethyl-4-piperidinyl) ester; tetrakis-(2,2,6,6-tetramethyl-4-piperidyl)-1,2,3,4-butane tetracarboxylate; 7-oxa-3,20-diazadispiro(5.1.11.2) heneicosan-20-propanoic acid, 2,2,4,4-tetramethyl-21-oxo, dodecyl ester; N-(2,2,6,6-tetramethyl-4-piperidinyl)-N′-amino-oxamide; o-t-amyl-o-(1,2,2,6,6-pentamethyl-4-piperidinyl)-monoperoxi-carbonate; β-alanine, N-(2,2,6,6-tetramethyl-4-piperidinyl), dodecylester; ethanediamide, N-(1-acetyl-2,2,6,6-tetramethylpiperidinyl)-N′-dodecyl; 3-dodecyl-1-(2,2,6,6-tetramethyl-4-piperidinyl)-pyrrolidin-2,5-dione; 3-dodecyl-1-(1,2,2,6,6-pentamethyl-4-piperidinyl)-pyrrolidin-2,5-dione; 3-dodecyl-1-(1-acetyl,2,2,6,6-tetramethyl-4-piperidinyl)-pyrrolidin-2,5-dione; (Sanduvar® 3058 from Clariant, MW=448.7); 4-benzoyloxy-2,2,6,6-tetramethylpiperidine; 1-[2-(3,5-di-tert-butyl-4-hydroxyphenylpropionyloxy)ethyl]-4-(3,5 -di-tert-butyl-4-hydroxylphenyl propionyloxy)-2,2,6,6-tetramethyl-piperidine; 2-methyl-2-(2″,2″,6″,6″-tetramethyl-4″-piperidinylamino)-N-(2′,2′,6′,6′-tetra-methyl-4′-piperidinyl) propionylamide; 1,2-bis-(3,3,5,5-tetramethyl-2-oxo-piperazinyl) ethane; 4-oleoyloxy-2,2,6,6-tetramethylpiperidine; and combinations thereof. Other suitable low molecular weight hindered amines are described in U.S. Pat. Nos. 5,679,733 to Malik, et al.

Other suitable light stabilizers may include UV absorbers, such as benzotriazoles or benzopheones, which can absorb ultraviolet light energy. Suitable benzotriazoles may include, for instance, 2-(2-hydroxyphenyl)benzotriazoles, such as 2-(2-hydroxy-5-methylphenyl) benzotriazole; 2-(2-hydroxy-5-tert-octylphenyl)benzotriazole (Cyasorb® UV 5411 from Cytec); 2-(2-hydroxy-3,5-di-tert-butylphenyl)-5-chlorobenzo-triazole; 2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-5-chlorobenzotriazole; 2-(2-hydroxy-3,5-dicumylphenyl)benzotriazole; 2,2′-methylenebis(4-tert-octyl-6-benzo-triazolylphenol); polyethylene glycol ester of 2-(2-hydroxy-3-tert-butyl-5-carboxyphenyl)benzotriazole; 2-[2-hydroxy-3-(2-acryloyloxyethyl)-5-methylphenyl]-benzotriazole; 2-[2-hydroxy-3-(2-methacryloyloxyethyl)-5-tert-butylphenyl]benzotriazole; 2-[2-hydroxy-3-(2-methacryloyloxyethyl)-5-tert-octylphenyl]benzotriazole; 2-[2-hydroxy-3-(2-methacryloyloxyethyl)-5-tert-butylphenyl]-5-chlorobenzotriazole; 2-[2-hydroxy-5-(2-methacryloyloxyethyl)phenyl]benzotriazole; 2-[2-hydroxy-3-tert-butyl-5-(2-methacryloyloxyethyl)phenyl]benzotriazole; 2-[2-hydroxy-3-tert-amyl-5-(2-methacryloyloxyethyl)phenyl]benzotriazole; 2-[2-hydroxy-3-tert-butyl-5-(3-methacryloyloxypropyl)phenyl]-5-chlorobenzotriazole; 2-[2-hydroxy-4-(2-methacryloyloxymethyl)phenyl]benzotriazole; 2-[2-hydroxy-4-(3-methacryloyloxy-2-hydroxypropyl) phenyl]benzotriazole; 2-[2-hydroxy-4-(3-methacryloyl-oxypropyl)phenyl]benzotriazole; and combinations thereof. Exemplary benzophenone light stabilizers may likewise include 2-hydroxy-4-dodecyloxybenzophenone; 2,4-dihydroxybenzophenone; 2-(4-benzoyl-3-hydroxyphenoxy) ethyl acrylate (Cyasorb® UV 209 from Cytec); 2-hydroxy-4-n-octyloxy)benzophenone (Cyasorb® 531 from Cytec); 2,2′-dihydroxy-4-(octyloxy)benzophenone (Cyasorb® UV 314 from Cytec); hexadecyl-3,5-bis-tert-butyl-4-hydroxybenzoate (Cyasorb® UV 2908 from Cytec); 2,2′-thiobis(4-tert-octylphenolato)-n-butylamine nickel(II) (Cyasorb® UV 1084 from Cytec); 3,5-di-tert-butyl-4-hydroxybenzoic acid, (2,4-di-tert-butylphenyl) ester (Cyasorb® 712 from Cytec); 4,4′-dimethoxy-2,2′-dihydroxybenzophenone (Cyasorb® UV 12 from Cytec); and combinations thereof.

When employed, light stabilizers, emulsifiers, protective colloids, initiators, can be partly included in the initial charge and partly metered in, or metered in completely during the implementation of the polymerization. The metering may take place separately or together with at least one monomer in the form of a monomer emulsion. Residual monomer can also be removed following the end of the polymerization, using known methods, by post-polymerization, generally by means of post-polymerization initiated using redox systems. Volatile residual monomers may also be removed by means of distillation, typically under reduced pressure, and, where appropriate, with inert entraining gases such as air, nitrogen or steam passed through or over the product.

The resultant copolymer dispersion will typically possess a solids contents of from about 20 wt. % to about 70 wt. %, such as from about 40 wt. % to about 60 wt. % although, as discussed below, maybe diluted before being applied to the textile fibers. The polymer typically has a glass transition temperature less than 70° C. so that the flexibility of the fibers is not substantially restricted. Moreover, the polymer also typically has a glass transition temperature of more than -50° C. to minimize tackiness. In some embodiments, the polymer has a glass transition temperature from about −30° C. to about +50° C., preferably from about −15° C. to about +30° C.

Colorant Medium

The colorant medium employed in the present dyeing process comprises a mixture of the above-described copolymer dispersion with one or more disperse dyes, generally in an amount such that the colorant medium contains from about 0.01 wt % to about 15 wt % of the disperse dye material. More preferably, the colorant medium can contain from about 0.5 wt % to about 5.0 wt % of the disperse dye material. The lower concentrations of the dye in the colorant medium are useful for tinting operations. Higher dye concentrations, of course, produce dyed cotton fibers, yarns, fabrics and garments having more intense color.

In addition to the disperse dye material and copolymer binder, the aqueous colorant medium can optionally contain various fiber and fabric treating adjuvants. Such adjuvants can include, for example, optical brighteners, fabric softeners, antistatic agents, antibacterial agents, anti-wrinkling agents, ironing aids, flame-retardants, enzymes, UV stabilizers, anti-foaming agents, perfumes, and the like.

Before being used to dye textile fibers, the colorant medium is typically diluted with water to a solids content from about 2 wt % to about 10 wt %, more preferably from about 3 wt % to about 6 wt % and adjusted to a pH in the range from about 2 to about 8, such as from about 4 to about 7.

Dyeing Process

The dyeing process described herein allows the continuous dyeing of textile fibers in which the colorant medium described above is applied to the textile fibers in a single padding operation.

Depending on the nature of the textile fibers being dyed, in some cases it may be desirable to initially subject the fibers to one or more known pre-treatment steps to enhance to receptivity of the material to the dyeing process. For example, pre-treating with enzymes is known to remove size and to improve the wettability of textile fibers. Such pre-treatments are conveniently effected by passing the textile fibers through one or more pre-treatment baths and then drying the pre-treated fibers on heated rollers before the material contacts the colorant medium.

The colorant medium comprising the disperse dye and the copolymer binder dispersion is loaded into a dye bath or reservoir of a continuous padding machine and the pre-treated textile fibers are passed through the bath to deposit the colorant medium at least on the surface of the fibers. After leaving the dye bath, the fibers with the colorant medium deposited thereon are drawn between padding rollers which squeeze the fibers and the liquid taken up with the fibers to distribute the colorant medium through the fibers.

It is found that the colorant medium is exhausted into the textile fibers substantially instantaneously in the dye bath, which is surprising since disperse dyes normally require a significant time to exhaust into textile substrates. As a result, the padding process can be operated at or near ambient conditions, with the bath temperature generally being from about 10° C. to about 50° C., and at commercially attractive padding rates. For example, in one embodiment, the continuous padding operation is run at a pad pressure (i.e. pressure between the pad rollers) from about 50 to about 250 kPa and at a pad speed (i.e. rate of passage of the textile fibers between the pad rollers) of from about 1 to about 70 m/minute. After passage through the padding rollers the colorant impregnated textile fibers typically contain from about 20 to about 120 wt %, preferably from about 50 to about 80 wt %, of the aqueous colorant medium on a liquid basis.

After the colorant impregnated textile fibers have left the padding rollers, the combination is subjected to drying and/or curing conditions which are effective to dry the fibers and cure the copolymer binder so that the binder assists in bonding the disperse dye to the fibers. In the case of cotton fibers, the curing typically serves to chemically anchor the copolymer to the cotton fibrous material via reaction of the copolymer with at least a portion of the hydroxyl moieties of the cellulose component of the cotton fibers. Such chemical reaction can occur via a cross-linking mechanism with the cross-linkable co-monomers which will generally form part of the emulsion copolymer as hereinbefore described. Curing of the fiber/colorant combination also will generally promote some self-cross-linking of the copolymer within the fibrous cotton materials as well.

Curing conditions for the fiber/colorant combination will generally involve heating the combination to elevated temperatures of from about 100° C. to about 200° C. for a period (dwell time) of from about 0.2 to about 4 minutes. More preferably, the fiber/copolymer combination can be cured by using temperatures of from about 130° C. to about 170° C. for a period (dwell time) of from about 0.5 to about 3 minutes. Where the textile fibers are in the form of a continuous length of fabric, the curing is conveniently conducted by passage of the dyed fabric through an oven while the fabric is held in a stenter frame. The dried and cured fabric can then be wound onto a storage roll to produce a final dyed product without additional treatment steps.

The padding and curing conditions are desirably be selected so that the final dyed fiber/dye/copolymer combination contains from about 0.1 to about 10 wt %, preferably from about 1 to about 8 wt %, more preferably from about 3 wt % to about 6 wt %, of the copolymer on a dry basis based on the combined weight of the copolymer and textile fiber material.

Dyed Cotton Fibrous Materials

As noted, the dyed fibers produced by the dyeing method described herein can be in a wide variety the forms. The fibers can be in the form of single ply or multi-plied yarns. Cotton staple fibers which form such yarns typically range from about 1.0 to about 3.0 denier per filament (dpf) and have a staple length range of from about 8.0 cm.

Cotton yarns can be fashioned into cotton fabrics for dyeing in accordance with the method herein by any conventional technique. The dyeing method herein is compatible with cotton fabrics having a wide range of fabric basis weights. Cotton fabrics will typically have a basis weight ranging from about 0.2 to about 7.0 g/m².

Weaving is a common method for making cotton yarn into cotton fabrics. The woven cotton fabrics which can be dyed in accordance with the dyeing method described herein include, for example, those of a basic weave, satin weave, twill weave, ripstop weave or basket weave.

Cotton yarns can also be knitted to provide as variety of knitted fabric types prior to being dyed in accordance with the dyeing method herein. Knitted cotton fabrics can be of the weft knit type, including double knits, jersey knits, rib knits or pique knits. Knit cotton fabrics may also be of the warp type, including tricot knits or raschel knits.

Yarns and fabrics can, of course, also be fashioned into end use products such as garments, apparel, upholstery, linens, etc. prior to being dyed in accordance with the dyeing method herein. No matter which form the dyed cotton fibers take, the dyeing method described herein will produce dyed cotton fibers and articles similar to those prepared by ring-dyeing techniques. In such dyeing, only the external surfaces of the copolymer-treated cotton fibers herein are colored by the disperse dye. The interior of the fibers remains un-dyed and un-colored since the disperse dyes used herein do not penetrate beyond the copolymer-treated fiber surface.

Typically, even with cotton fibers, the dispersed dyed textile fibers produced by the present process exhibit at least one and typically all of the following properties:

a wet crockfastness as determined according to AATCC Test Method 8 of at least 3.5 and preferably at least 4;

a lightfastness as determined according to AATCC Test Method 16, Option 3 (using a xenon light source for 20 hours) of at least 4 and preferably at least 4.5; and

a washfastness as determined according to AATCC Test Method 61 (IIA) of at least 3 after 5 accelerated wash cycles.

The invention will now be more particularly described with reference to the following non-limiting Examples.

Example 1

20 g of a self cross-linking vinyl acetate/ethylene copolymer dispersion sold under the trade name TruModa® 741, and having a solids content of about 50 wt %, was first diluted with 79.8 g of water. 0.2 g of a fluorescent disperse dye, M. Dohmen Dorospers Luminous Yellow 10DG (CI Disperse #184.1), was then gradually added to the diluted dispersion while the latter was stirred with mild heating (38° C.). Acetic acid was then added to achieve a solution pH of 4

The mixture was then poured into the dam of a Mathis padding machine and the roller pressure was set to 25 psi (172 kPa). A cotton 3x1 twill fabric, weighing about 220 grams per square meter, was then fed through the padding mangle and subsequently dried at 130° C. for 3 minutes. The wet pickup of the fabric was approximately 70%, so that the total solid add on was approximately 7 wt %. Upon drying, the mixture of dyestuff and copolymer binder had migrated towards the surface of the fabric, producing a brilliant fluorescent yellow color with 145% maximum reflectance and a maximum K/S value of 6.0.

Upon conducting AATCC test method 61-IIA (laundering fastness), the gray scale color change of the fabric was given as a 4-5 by a DataColor spectrophotometer. Upon conducting AATCC test method 8 (wet crock fastness), Evaluation Procedure 12, the gray scale for staining of the fabric was given as a 4-5 by a DataColor spectrophotomer. Upon conducting an AATCC test method 8 (dry crock fastness), Evaluation Procedure 12, the gray scale for staining of the fabric was given as a 5 by a DataColor spectrophotometer.

Example 2

7.5 g of an alkyl acrylate-based dispersion supplied by Celanese under the trade name TruModa® 721 was first diluted with 88.0 g of water. 2.0 g of disperse dye was then gradually added to the diluted dispersion while the latter was stirred with mild heating (38° C.). 2.5 g of a non-ionic silicone softener was then gradually added to the diluted dispersion with continued stirring. Acetic acid was then added to achieve a solution pH of 4. The mixture was then poured into the dam of a commercial padding machine and the roller pressure was set to 20 psi (138 kPa). A cotton 300 thread count sheeting fabric, weighing about 120 grams per square meter, was then fed through the padding mangle at a speed of 20 meters/minute and subsequently dried at 130° C. in the first 15 meters of a 30 meter stenter frame, and dried at 150 C in the final 15 meters of the same frame. Before passing through the stenter frame, the fabric was exposed to an infra-red pre-drier. The wet pickup of the fabric was approximately 65%, so that the total solid add on was approximately 4.0 wt %. Upon drying, the mixture of dyestuff and copolymer binder had migrated towards the surface of the fabric, producing a very level coloration in the fabric. Due to the addition of the softener in the bath, the fabric also exhibited a very soft hand feel. Upon conducting AATCC test method 8 (wet crock fastness), Evaluation Procedure 12, the gray scale for staining of the fabric was given as a 4 by a DataColor spectrophotomer.

Upon conducting an AATCC test method 8 (dry crock fastness), Evaluation Procedure 12, the gray scale for staining of the fabric was given as a 4-5 by a DataColor spectrophotometer. 

1. A process for dyeing textile fibers, the process comprising; (a) providing at least one dye bath comprising a colorant medium comprising a disperse dye and an aqueous dispersion of a copolymer selected from vinyl ester-based copolymers, alkyl acrylate copolymers, alkyl methacrylate copolymers and mixtures thereof; (b) passing the textile fibers through the at least one dye bath to deposit the colorant medium at least on the surface of the fibers; (c) passing the fibers with the colorant medium deposited thereon between padding rollers to distribute the colorant medium through the fibers; and then (d) heating the fibers to cure the copolymer and bond the disperse dye to the fibers.
 2. The process of claim 1, wherein the textile fibers comprise natural fibers, preferably cellulosic fibers, more preferably cotton fibers, optionally together with synthetic fibers.
 3. The process of claim 1, wherein the copolymer comprises vinyl acetate and ethylene.
 4. The process of claim 1, wherein the copolymer comprises from 60 wt % to 95 wt % of vinyl acetate and from 5 wt % to 40 wt % of ethylene, based on total weight of monomers therein.
 5. The process of claim 1 any preceding claim, wherein the copolymer comprises an alkyl acrylate and/or an alkyl methacrylate containing 1 to 12, preferably 1 to 10, carbon atoms in the alkyl group.
 6. The process of claim 5, wherein the copolymer further comprises acrylonitrile.
 7. The process of claim 1 any preceding claim, wherein the copolymer comprises less than 25 wt % polyester.
 8. The process of claim 1 any preceding claim, wherein the colorant medium comprises from 0.01 wt % to 15 wt % of the disperse dye.
 9. The process of claim 1, wherein the colorant medium has a solids content from about 2 wt % to about 10 wt %.
 10. The process of claim 1, wherein the colorant medium has a pH in the range from 2 to
 8. 11. The process of any claim 1, wherein the temperature of the colorant medium during step (b) is from 10° C. to 50° C.
 12. The process of any claim 1, wherein the textile fibers are passed through the dye bath at a rate of from 1 m/min to 70 m/min.
 13. The process of claim 1, wherein the padding rollers apply a pressure from 50 to 250 kPa to the textile fibers during step (c).
 14. The process of claim 1, wherein the heating (d) is conducted at a temperature from 100° C. to 200° C. for a period (dwell time) of from 0.2 to 4 minutes.
 15. The process of claim 1, wherein heating (d) produces a dyed textile fiber product comprising from 0.1 to 10 wt % of the copolymer on a dry basis based on the combined weight of the copolymer and textile fibers.
 16. The process of claim 1, wherein the fibers are continuously passed from step (b) to step (d). 